The present invention relates to the field of communication systems, and more particularly to an apparatus and method operable to facilitate signal processing using variable blazed grating based elements.
As optical systems continue to increase the volume and speed of information communicated, the need for methods and apparatus operable to facilitate high speed optical signal processing also escalates. Various devices and methodologies have been developed to provide numerous signal processing capabilities on optical signals. Some of these devices attempt to control a diffraction of an input optical signal to facilitate basic signal processing functions.
One such approach, known as a variable blazed grating, implements a movable diffraction grating that can be selectively displaced to cause a majority of the diffracted input signal to travel in a particular direction. Co-pending application Ser. No. 09/776,051, entitled xe2x80x9cVariable Blazed Gratingxe2x80x9d, filed Feb. 2, 2001 provides a number of examples of such devices.
In some aspects of operation, variable blazed gratings operate to reflect or diffract signals along the same signal path as that of an optical signal being input to the grating. If left unchecked, the input and output signals traveling on the same path can interfere with one another, or the output signal could cause complications to the source of the input signal.
The present invention recognizes a need for a method and apparatus operable to economically facilitate high speed optical signal processing. In accordance with the present invention, apparatus and methods operable to facilitate optical signal processing are provided that substantially reduce or eliminate at least some of the shortcomings associated with prior approaches.
In one aspect of the invention, an optical switching element comprises a variable blazed grating operable to receive and reflect one or more input signals while the grating remains in a first position and to receive and diffract one or more input signals while the grating remains in a second position. The switching element further comprises a first circulator operable to receive from the variable blazed grating a first output signal traveling approximately along the path of an input signal to the grating but in an approximately opposite direction to that input signal, and to redirect the first output signal from the path of the input signal.
In still another aspect of the invention, a method of processing optical signals using a variable blazed grating comprises receiving at a variable blazed grating residing in a first position one or more optical input signals and displacing the grating between a first position and a second position. The method further comprises reflecting the input signals while the blazed grating remains at the first position and, for each input signal received, diffracting a majority of that input signal in a particular direction while the grating remains at the second position. The method still further includes receiving from the grating a first output signal at a first circulator disposed in the path of an input signal, the first circulator operable to redirect the first output signal from the path of the input signal.
In yet another aspect of the invention, an optical switching element comprises a variable blazed grating operable to receive a first optical input signal from a first input and to reflect the first signal toward a first output while the grating remains in a first position, the variable blazed grating further operable to undergo a displacement to a second position, the displacement resulting in a diffraction of a majority of the first input signal toward a second output. The optical switching element is operable to switch between the first position and the second position and at a rate optimized for a specified packet size.
In another aspect of the invention, a system operable to process multiple wavelengths of light using variable blazed gratings comprises a wavelength division demultiplexer operable to receive an optical signal comprising a plurality of wavelength signals and to separate at least some of the plurality of wavelength signals from others of the wavelength signals, and an array of variable blazed grating devices. Each variable blazed grating device is operable to process at least one of the wavelength signals by reflecting the received signal in one direction while a grating of the variable blazed grating device resides in a first position and diffracting a majority of the received signal in a second direction while the grating resides in a second position.
In still another aspect of the invention, a method of processing a plurality of wavelength signals comprises separating an optical input signal comprising a plurality of wavelength signals into a plurality of input wavelength signals, each carrying one or more wavelengths of light, and communicating at least some of the input wavelength signals to an array of variable blazed gratings for processing. Each variable blazed grating device having a grating operable to be displaced between at least a first position and a second position. For each input wavelength signal received by the array, the method includes positioning the grating in either the first or the second position, reflecting in a first direction each received input wavelength signal from the receiving grating while the receiving grating resides at the first position, and diffracting a majority of each received input wavelength signal in a second direction while the receiving grating resides at the second position.
In yet another aspect of the invention, a variable blazed grating based optical add/drop multiplexer comprises a variable blazed grating oriented in a first position and operable to receive a first optical signal and a second optical signal, while the grating remains in a first position the blazed grating operable to reflect the first signal toward a first circulator and to reflect the second signal toward a second circulator. Either the first or the second circulator is coupled to an output port and the other is coupled to a drop port. The variable blazed grating is operable to undergo a selective displacement to a second position, the displacement resulting in a diffraction of a majority of the first input signal toward the second circulator and a diffraction of a majority of the second input signal toward the first circulator.
In another aspect of the invention, a method of facilitating optical add/drop multiplexing using a blazed grating comprises receiving a first optical signal and a second optical signal at a variable blazed grating residing in a first position. The method further comprises reflecting the first signal toward a first circulator and the second signal toward a second circulator while the mirror strips remain at the first position, wherein either the first or the second circulator is coupled to an output port and wherein the other is coupled to a drop port. The method still further comprises displacing the grating from the first position to a second position, and while the grating resides at the second position, diffracting a majority of the first signal in one direction toward the second circulator and diffracting a majority of the second signal in another direction toward the first circulator.
In still another aspect of the invention, a blazed grating based wavelength division add/drop multiplexer comprises a wavelength division demultiplexer operable to receive an optical input signal comprising a plurality of wavelength signals and to separate the plurality of wavelength signals from one another and an array of blazed grating based add/drop multiplexers each operable to receive at least one of the wavelength signals. Each add/drop multiplexer comprises a variable blazed grating oriented in a first position and operable to receive at least one of the wavelength signals and an added signal, while the grating remains in a first position the blazed grating operable to reflect the received wavelength signal toward a first circulator and to reflect the added signal toward a second circulator, wherein either the first or the second circulator is coupled to an output port and the other is coupled to a drop port. The variable blazed grating is operable to undergo a selective displacement to a second position, the displacement resulting in a diffraction of a majority of the received wavelength signal toward the second circulator and a diffraction of a majority of the added wavelength signal toward the first circulator.
In yet another aspect of the invention, a blazed grating based electro-optic switching system comprises a fiber optic tap operable to receive an optical signal having header information and payload information and to form a first signal copy comprising at least the header information and a second signal copy comprising at least the payload information. The system further comprises an electronic processor operable to receive the first signal copy and to perform electronic processing on the header information, and an array of blazed grating based optical switch elements operable to receive the first and second signal copies and to perform an optical switching operation on the first and second signal copies.
Depending on the specific features implemented, particular aspects and embodiments of the present invention may exhibit some, none, or all of the following technical advantages. One aspect of the present invention provides an efficient and cost effective mechanism for facilitating high speed signal processing using a diffraction based technology while reducing or eliminating at least some of shortcomings typically associated with diffraction based signal processing. For example, particular embodiments of the invention facilitate diffraction based signal processing that maintains good contrast ratios without requiring the additional beam collection and/or combining technology often associated with other approaches.
One aspect of the invention utilizes optical circulators in combination with variable blazed gratings to redirect output signals from the path of incoming signals. This facilitates enhanced system performance by reducing or eliminating interference between input and output signals, while avoiding at least some of the losses typically associated with other approaches.
One aspect of the invention facilitates multiple wavelength signal processing in a multiple-wavelength system by combining wavelength demultiplexers with variable blazed grating switching elements. This technique applies to a number of signal processing applications, such as optical gain equalization, add/drop multiplexing, and optical switching systems.
The invention facilitates fabrication of arrays of blazed-grating based elements at a nominal incremental cost over that of producing a single element. This aspect of the invention facilitates construction of, for example, gain equalizers and wave-division add/drop multiplexers capable of processing numerous wavelengths for a small incremental cost over a single stage of elements. This provides significant cost savings in processing signals carrying information on multiple channels or wavelengths.
Other technical advantages are readily apparent to one of skill in the art from the attached figures, description, and claims.